No, an 80% chance of rain does not necessarily mean that it will rain all day. The probability of rain indicates the likelihood that measurable rainfall will occur at some point within a specified area or time frame.
An 80% chance of rain suggests that there is a high probability that rain will occur, but it does not provide information about the duration or intensity of the rain. It could mean that there is a likelihood of scattered showers throughout the day, or it could mean that there is a higher chance of rain during a specific time period.
Weather forecasts often provide additional details such as the timing, duration, and intensity of rain events, which can give you a better idea of what to expect. It's always a good idea to check a more detailed forecast or consult a local weather source for specific information about rain patterns in your area.